21981672981738 has 24 divisors (see below), whose sum is σ = 47868719343588. Its totient is φ = 7290030293952.

The previous prime is 21981672981691. The next prime is 21981672981739. The reversal of 21981672981738 is 83718927618912.

21981672981738 is a `hidden beast` number, since 2 + 1 + 9 + 8 + 167 + 298 + 173 + 8 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 14728578355089 + 7253094626649 = 3837783^2 + 2693157^2 .

It is not an unprimeable number, because it can be changed into a prime (21981672981739) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3099499131 + ... + 3099506222.

Almost surely, 2^{21981672981738} is an apocalyptic number.

21981672981738 is an abundant number, since it is smaller than the sum of its proper divisors (25887046361850).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21981672981738 is a wasteful number, since it uses less digits than its factorization.

21981672981738 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6199005558 (or 6199005555 counting only the distinct ones).

The product of its digits is 146313216, while the sum is 72.

The spelling of 21981672981738 in words is "twenty-one trillion, nine hundred eighty-one billion, six hundred seventy-two million, nine hundred eighty-one thousand, seven hundred thirty-eight".